Low resistance fluid flow switch



Feb. .14, 1933. w. R. wALKE 1,897,455

LOW RESISTANCE FLUID FLOW SWITCH Filed March 3, 1931 INVENTOR Patented Feb. 14, 1933 UNITED STATES PATENT OFFICE I WARREN B. WALKER, OF SHORT HILLS, NEW JERSEY, ASSIGNOR TO GENERAL ELEC- TRIO VAPOR LAMP COMPANY, OI HOBOKEN, NEW JERSEY, A CORPORATION 01 NEW JERSEY LOW RESISTANCE FLUID FLOW SWITCH Application filed larch 3,

The present invention relates to fluid flow switches, and particularly to fluid flow switches which are adapted for use in circuits carrying relatively large currents.

The invention consists in a fluid flow switch of novel construction, and in the novel me.hd of operating the same, as hereinafter set forth and claimed.

A particular object of the invention is to provide a fluid flow switch which will have a high current capacity. Another object of the invention is to provide a switch having a low internal resistance. A further object of my invention is to provide a switch of extremely simple construction having the aforesaid characteristics. Still another object of my. invention is to provide a novel method of operating a fluid flow switch. Other objects and advantages of my invention will-appear from the following detailed specification, or from an inspection of the accompanying drawing.

The current rating of electrical switches is determined, as is well known, by two factors; one the current which they can safely interrupt, and the other the current which they can continuously carry without undue heating due to the resistance thereof.. In switches of the fluid flow ty e the emphasis has been on the first of these ihctors, hence in this type of switch the metallic inleads have invariably been spaced a considerable distance apart, in order to permit the arc of rupture to be drawn out to a suflicient length to extinguish it. This construction obvious- 1y necessfates the use of a relatively lon fluid path to complete the circuit throug the switch when it is in a closed circ'uit osition. A long fluid path is, however, high y undesirable from the standpoint of the second factor mentioned above, due to the fact that any of the fluids which are ordinarily used have a relatively high specific resistance. For example, mercury, thefluid almost uni- .yersally used, has a specific resistance which is "approximately twenty times as great as that of-tungsten, and sixty times that of copper. Hence from the. standpoint of minimum internal resistance, and thus of minimum is obvious that the fluid 1931. Serial No. 519,834.

the result that there hasbeen heretofore a more or less definite limit to the capacity of commercially practical fluid flow switches.

I have now discovered that this limitation can be overcome by means of a novel construe tion of my invention, which operates in a It would thus appear that addi unique manner to provide a relatively short fluid path of low resistance during the time that the circuit is closed, and a relatively long fluid path at the moment that the circuit is opened". This new resultis obtained by providing the switch with inleads which are so arranged that as the fluid flow takes place a circuit is first closed therebetween through a relatively long fluid path, while upon further flow of said fluid a parallel circuit is closed therebetween through a relatively short fluid path, these circuits being opened in the re verse order when the circuit through the switch is to be interrupted. With this novel construction it is obvious thatthe fluidpath which is opened to interrupt the current may bemade-as long as desired, despite the fact that the other path, utilized to conduct the current when the switch is in the closed position, is extremely short. Thus I have succeeded in combining the desirable characteristics of a switch having a short fluid ath and those of a switch having a long uid ath in a single switch of unique construction.

y new construction is, moreover, extremely simple, requiring only a suitable extension of an inlead, or the provision of an auxiliary inlead, and hence 'my new switch is not only circiiitposition,

of the switch of Fig. 1, in which a main inlead ig. 4 iza sectional view of a modification also performs the function of the auxiliary inlead, the switch being shown in a closed circuit position,

Fig.5 is a similar view of another modification of the switch of Fig. 1,

, Fig. 6 is a sectional view of a preferred embodiment of my invention,

with said inlead 6 and with an inlead 8, simi- Fig 7T:isa sectional view of the switch of 6, taken on the line 7-7 and Fig. 8 shows another modification of the.

switch of Fig. 1, in which a resistance is included in the lead between the auxiliary inlead and the main inlead.

In this drawing, with particular reference to the switch shown in Figs. 1-3, the closed tubular body 1, which is preferably made of a suitable arc resisting vitreous material, such as a boro-silicate glass, although other vitreous materials may be used when desired, has a cup 2 formed in the bottom thereof adjacent to one end which retains a mercury pool 3. An inlead 4 of sufficient diameter to carry the rated current without undue heating, and which may be conveniently made of tungsten when the body 1 consists of a borosilicate glass, is sealed into said cup 2. Said inlead-4 preferably extends upwardly as far as is consistent with its remaining below the surface of the mercury pool 3. Another cup 5 is formed in the bottom of the tubular bod 1 at some distance from the cup 2, into whic is sealed an inlead 6 of tungsten or other suitable metal. Since this inlead is not called upon to carry the rated current, except for short intervals, it need not be of as large diameter as the inlead 4. A pool of mercury 7 is enclosed within the tubular body'l, said P mercury being present in suflicient quantity to make simultaneous contact, when the switch is in the position shown in Fig. 3-,

lar in nature to the inlead4, which is sealed through the top 0 the tubular body 1 at a point directly opp site said inlead 4 and which terminates at a point'which is just above the surface of the mercury pool 7 at the moment of its merger with themercury pool 3.- Said inlead 8 is permanently connected with the inlead 6 by means of a suit aeeaate able conductor 9. The switch body 1 is preferably filled with an arc suppressing atmosphere, such as hydrogen, ammonia or the like, at a suitable pressure.

g In the switch of Fig. 4 a similar closed tubular body 11 has a cup 12 formed 'in the bottom thereof adjacent to one end, in which is retained a mercury pool 13. An inlead 14 is sealed into said cup 12, terminating just below the surface of the pool 13, this construction all being identical with thatof the switch previously described. A second cup 15 is formed in the bottom of the tubular body 11 at "some distance from the cup 12,.

an inlead 16 of large current capacity being sealed into said cup 15. Said inlead 16 con tinues upwardly through said cup 15 to a point near the top of the tubular bod 11, thence longitudinally through'said b y to a point above the inlead 14, at which point it turns downwardly toward said inlead 14, terminating at a point a short distance above said inlead. A mercury pool 17 sufficient in quantity to simultaneously connect with the inlead 16 at the cup 15 and at its downturned end at one position of the switch is enclosed within the tubular body 11. A suitable arc suppressing atmosphere, such as hydrogen, is also preferably sealed within said tubular body.

With reference to the modification shown in Fig. 5, the closed tubular body 21 has a cup 22 in the bottom thereof adjacent to one end, in which is retaineda mercury pool 23. An' inlead 24 of large current capacity is sealed into said cup 22, terminating just below the surface of the pool 23. A second cup 25 is formed in the bottom of said tubular body 21 as close as is practicable to the cup 22, a pool of mercurv 26 being retained therein. ,An-inlead 27 of large current capacity is likewise sealed into said cup 25, said inlead terminating just beneath the surface of the pool 26. A third cup 28 is formed in the bottom of'the tubular body-21 at some distance from the cup 25, into which is sealedan inlead 29, which need not be of as large current carrying capacity as the inleads 24 and'27. A suitable conductor 30 permanently connects the inleads 24 and 29. A suflicient quantity of mercury 31 is enclosed with- -in the tubular body 21 to make contact simultaneously with the mercury pools 23, 26 and the inlead 29 at one position of the. switch,

and a suitable arc suppressing atmosphere, preferably hydrogen, is sealed within said switch. Y

A switch having a preferred construction is illustratedin Figs. 6 and 7. In this switch the closed tubular body 35 has the two inleads 36 and 37 sealed into one end thereof through a common pinch seal. A .cup 38 is formed in the bottom of said body 35 as near -as'is practicable to the aforesaid seal. A re fractory lining 39 of suitable vitreous material, such as fused silica, porcelain, or the like extends lon 'tudinally within the tubular body 35, said ining 39 having a cup 40 formed therein near one end which extends into the cup 38. Said lining is preferably of such a shape, as shown in Fig. 7, that it can be 1nserted within the tubular body in a completely formed condition, the lower portion thereofconforming to the curvature of sald body 35, while the upper portion" thereof is somewhat flattened, so that the maximumdiameter of said lining 39 at the cup 40 is less than the internal diameter of the tubular body 35. Said lining 39 is held in its proper position within the tubular body 35 by the inlead 36 which extends into the, end of said lining which is adjacent to the seal, and then turns downwardly, terminatin in the cup 40. The inlead 37, which extends ongitudinally through the tubular body 35 above said 11ning 39 and then turnsgback and downwardly within the opposite end of said lining, terminating near the bottom thereof at some distance from the cup 40, likewise assists in retaining the lining 39 in the desired position. A quantity of mercury 41 which is sufficient to make contact simultaneously with the inlead 37 at a point near the seal and with the end of said inlead is enclosed within said tubular body 35. An arc suppressing atmosphere, such as hydrogen, ammonia, or the like at a suitable pressure is preferably sealed within said tubular body 35.

The switch of Fig. 8 is in most respects similar to that of Figs. 1-3. Aresistance 10. is

connected in series with the conductor 9 of this switch, however, between the inleads 6 and 8. A refractory lining 45 of porcelain, lavite, fused silica or the like extends longitudinally within the tubular body 1 from a point near the cup 2 to a point near the cup 5. When this lining has a suitable co'-' efficient of expansion it is fused directly to the body 1, as shown. Other refractory materials may bejused, however, in which case the lining 45 may be cemented to the body 1, or

the space therebetween may be packed with asbestos, spun glass or the like, or any other suitable method of mounting may be used. A somewhat larger quantit of mercury 7' is used and the inleads 4' an 8' are somewhat longer and shorter respectively in order to maintain the same relative position to the mercury levels as in the switch of Fig. 1.

In the use and operation of the switch of Figs. 1-3, assuming the switch to be in an open circuit position such as shown in Fig. 1, uion tllting the switch body 1 in a countercloc mercury pool 3 therein. A circuit 15 thereby closed from the inlead 8 through the conductor 9, inlead 6 and mercury 7 to the inlead 4, as shown in Fig. 2. 'Due to the small area and great length of the mercury path at this wise direction the mercury 001 7 flows .toward the cup 2, eventually merging with the inlead 8 through the mercury 7 to the inlead 4. Since the mercury 7 is still in contact with the inlead 6 at the time this new circuit is established there can obviously be no arc at i the making of the contact between the mercury pool 7 and the inlead 8, since said pool is i at substantially the same potential as said inlead. Due to the extremely large area and short length of the new fluid path the internal resistance of the switch is obviously very markedly reduced, to say a few percent of the initial value, hence very large currents may be continuously carried thereby without undue heating. For example, it has been found possible to carry currents of 50-100 amperes in switches of my novel construction having such dimensions that their current carrying capacity, if operated according to the prior art, would not be more than 25 am eres. Further tilting of the switch body 1 wi 1 not make any appreciable change in the operation of the switch, since the opening of the cir- Upon reverse movement of the switch of 1 Figs. 1-3, assuming that the switch body 1 has been tilted so far beyond the position shown in Fig. 3 as to open the circuit to inlead 6, it is obvious that the flow of the mercury 7 to again merge with the pool retained in the cup 5 will not cause any are of make, due to the absence of any appreciable potential between the mercury 7 and said pool. Further movement of the switch body 1 in a clockwise direction soon causes the level of the mercury 7 tofall away from the inlead 8, thereby opening-the direct circuit between the inleads 4 and 8. Since a circuit is still closed, however, from the inlead 4 to said inlead 8 through the mercury 7, inlead 6 and conductor 9, as shown in Fig. 2, it is obvious that said mercury 7 and said inlead 8 are maintained at substantially the away from t 1e cup 2, and to eventuall sepa-' rate from the mercury pool 3 retaine therein, the arc of rupture occurring between said H current rupturing capacity possessed by switches in which the circuit is ruptured between relatively remote fluid pools.

The switch of Fig. 4 operates in a similar manner. n As this switch is tilted in a counter-clockwise direction from the open circuit position in which it is shown the mercury pool 17 flows toward the cup 12, eventually merging withthe mercury pool 13 therein. A circuit is thereby closed from the inlead 14 through the mercury 17 to the inlead 16 at a point adjacent to the cup 15. Since this circuit includes a relatively long fluid path it is not adapted to continuously carry a large current. By further tilting of the switch body 11, however, the level of the mercury 17 is caused to rise, with respect to .the inner endof the inlead 16, until it comes into contact therewith. The fluid path between said inleads 14 and 16 is thereby great-- v1y decreased, so that the internal resistance of the switch is materia 1y reduced. Where the inlead 16 consists of tungsten, due to the ease with which it is sealed to theborosilicate glasses, the internal resistance of the switch may he still further reduced, if desired, by

making the portion of said inlead which extends within the switch envelope of a better electrical conductor, such as copper, the latter being preferably plated with nickel, chro .mium or the like in order to prevent contamination of the mercury by amalgamation.

" that there is no danger of this are striking. to any part of the inlead 16. It will thus be Uponmovement of the switch body 11 in the reverse direction the mercury 17 first falls away from the end of the inlead 16, but since the circuit is stillclosed to said inlead 16,

i albeit through a longermercury path, there obviously can be no arc of rupture between said mercury 17 and the end of said inlead. Upon further movement of the switch body 11 in a clockwise direction the mercury pool 17 will'sepa-rate from the mercury pool 13, opening the circuit through the switch, an arc thereupon occurring between said pools which is immediately quenched by the hydrogen atmosphere. Experience'has proven seen that this switch embodies the .advanta es of the switch of Figs. 1-3 in a switch hav ng but two inleads.

-The switch of Fig. 5 also operates in a manner similar to that of Figs. 13. As the switch body 21 is tilted in a counter-clockwise mercury 41 falls until direction from the open. circuit position 'in which it is shown the mercury 31. moves toward the cup 25, and eventually merges with the mercury pool 26 therein. A circuit'is thereupon closed from inlead 27 through a relatively long path in the mercury 31-to' the inlead 29, thence through the conductor 30 to the inlead 24. This circuit; being similar in fluid length to that through switches of the prior art, is obviously not adapted to continuously carry large currents. Hence provision is made for the mercury 17 ,to move further, upon further tilting of the switch body 1, until it merges with the mercury pool 23. A circuit is thereupon completed from theinlead 27 through a relatively short mercury path to the inlead 24. Upon movethe switch body 21 in a clockwise direction,

however, causes the mercury 31 to separate from the mercury pool 26, whereupon the circuit through the switch is interrupted, an are occurring between the mercury 31 and the mercury pool 26, this are being rapidly extinguished in a well known manner by the arc suppressing atmosphere. This switch thus operates in a manner analogous to the switch shown in Fig. 1. At the same time it has certain features of construction which render it especially desirable for some uses.

With the construction illustrated in Figs. '6 and 7 as the switch body 35 is tilted in a clockwise direction from the closed circuit position illustrated in Fig. 6 the level of the said mercury is no longer in contact with the inlead 37 at a point adjacent to the seal. The short fluid path between the inleads 36 and 37 is thereby opened. N o are ensues however, due to-the 'fact thata circuit is still closed between said inleads through a relatively long pathin the mercury 41 to the tip of the inlead 37. Further tilting of the switch in the same direction 41 from a pool thereof which is retained within the cup 40, whereby thecircuit through the switch is interrupted, arelatively long are ofrupture being permitted between the aforesaid pool'and the moving mercury bod 41, this are being rapidlysu pressed by the hydrogen atmosphere. The

refractory lining 39 effectively shields' the switch body 35 from this arc, and likewise prevents any possible striking of the arc of rupture. to an intermediate point on the inlead 37. When the sealed envelope of the switch is thus protected by a refractory linmg it is obvious that notfonly may very-large results in the separation of the mercurybody 7 itself can be constructed, where desired,

cheaper glass, such as lead or lime glass.

As shown in Fig. 8 the conductor 9 by winch the inleads 6 and 8 of the switch of F 1 1 are connected may have an apprec1a le resistance 10 connected therein. This resistance, which may result from formin the conductor 9 of resistance material, suc as nichrome, of suitable current carrying capacity, may be of a value which is commensurate with the impedance of the load which the switch controls, in which case the current that the switch must handle during the intermediate stage illustrated is materially reduced. More important, however, the current which the switch must interrupt is also reduced to say a half of the normal value. In operation, assuming the switch to be in a closed circuit position, upon tilting the switch in a'clockwise direction the mercury 7 flows away from the inlead 8, opening the short fluid path thereto from the inlead 4. The current is thereupon forced to traverse the longer path throu h the mercury 7 to the inlead 6, thence t rough the conductor 9 and resistance 10 to said in-' lead 8', the current being thereby eatly reduced. Despite the fact that a considl e rable potential difference is created between said inlead. 8 and the mercury 7 as a result of the voltage drop through the resistance 10 it is found that there is no arc of ru ture as the mercury 7' falls away from sai inlead 8'. Further tilting of said switch causes the circuit to be interrupted between the mercury pool 3 and the mercury 7', with a resulting arc therebetween. The intensity of this are is much reduced, however, due to the smaller current which is interrupted. The tubular body 1 is effectively shielded from this are, however, by the refractory lining 45. Upon closing the circuit throu h the switch the'circuit is first closed in an o vious manner through the resistance 10, and then directly from the inlead 4 to the inlead 8' through the desired short mercu path. Thus my new construction in ad ition to materially increasing the current carrying capacity of mercury switches, lends itself to increasing the rupturing capacity thereof. A switch of this construction is .thus especially adapted, both by reason of the reduced arc of rupture and of the refractory lining, to control extremely large currents of the order of hundreds of amperes. Or, where desired, this construction may be utilized'to permit the control of.relatively large currents in a switch whose envelope is made of one of the less expensive soft glasses, such as lead glass, lime glass, etc.

While I have illustrated my invention by reference to, several specific embodiments thereof it is to be understood that it is not limited thereto, but that various changes,

" with said mercury onl 1s closed and to open said shbrterfath before. --said long fluid path is interrupte 2. A mercury switch comprising a sealed envelope, mercury in said envelope, means to divide said mercury into two pools at will,

inleads sealed into said envelope and making contact with each of said pools and means to reduce the len h of the conducting mercury path to less t an the distance between the portions of said inleads which are in con-- tactiwith said mercury pools at the moment said pools are merged, said last mentioned means bein effective only after said pools have merged and before they are separated.

3. A mercury switch comprising a sealed tubular envelope, mercury in said envelope, an open ended lining within said envelope, a mercury retaining cup in said lining at a point near one end of said envelope, two in-. leads sealed into the same end of said envelope, one of said inleads extendin into said cup while the other inlead extends ongitudinally above said lining and then turns downwardly within said lining.

4. A mercury switch comprising a sealed envelope, mercury in said envelope, inleads sealed into said envelope and making contact at remote points when the circuit throug said switch is being opened or closed, one of said inleads being adapted to make an auxiliary contact with said mercury at a point close to a submerged part of the other inlead when said switch is in a closed circuit position.

5. A mercury switch comprising 'a sealed envelo e, .mercury in said envelope,'a cup in sai envelope near one end thereof, an inlead sealed into said cup, another inlead sealed into said envelo e at a point remote from said cup and-making contact with said mercury in both the open and the closed circuit position of said switch, the latter-inlead extending upwardly to a point near the top of said envelo e,'thence longitudinallivtherein to a point a ove the first mentione inlead, and thence downwardly to a point just above the level of the mercury retained in said cup.

6. A mercury switch comprising a sealed envelope, mercury in said envelo e, means to divide said mercury into two $00 at will, an inlead in contact with each 0 said ools, and a third inlead sealed into said enve ope, said 6 neonate third inlead extending toa point in proximity to one of said first mentioned inleads and being permanently connected to the other of said inleads, the relative position of said inleads being such that-the gap between said adjacent inleads is bridged by said mercury after said pools have been merged and reestablished before said mercury is again divided. I r

7. A mercury switch comprising a sealed envelope, mercury in said envelope, means to divide said mercury into two pools at will, an inlead in contact with eachof said pools, and a third inlead sealed into said envelope, said third inlead extending to a point in proximity to one of said first mentioned inleads and being permanently connected through a resistance to the other of said inleads, the relative position of said inleads being such that the gap between the inleads which are in proximity is bridged after said a pools have been merged and reestablished Y out the come" before said mercury is again divided.

Signed at Hoboken in the county'of Hudson and State of New Jersey this 2nd day of March A. D. 1931.

WARREN R. WALKER.

CERTIFICATE OF CORRECTION.

latent No.l,97,45. February l4, 1933. I wmmn. WALKER.

It is hereby certified that error appears in theprint ed specification-of the Page 4, line 87, strike inlead 29 and conductor30 there", and insert instead But-since the inleads 24 and 27" and that the said Let that the stamens",-

abovenumberedipitetttj requiring correction as. follows:

b p d ters Pateat e'hoa "reed", with this correction therein coniorut to the case in the Patent Office. 7

sa um-sequent: 18th day ofApril, A; n. 1933.

M. J. Moore Acting Commissioner of Patents. 

